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Upstream hash: speedup consistent hash init.

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Repeatedly calling ngx_http_upstream_add_chash_point() to create
the points array in sorted order, is O(n^2) to the total weight.
This can cause nginx startup and reconfigure to be substantially
delayed.  For example, when total weight is 1000, startup takes
5s on a modern laptop.

Replace this with a linear insertion followed by QuickSort and
duplicates removal.  Startup for total weight of 1000 reduces to 40ms.

Based on a patch by Wai Keen Woon.
This commit is contained in:
Roman Arutyunyan 2015-03-02 18:41:29 +03:00
parent de3adad807
commit bf7d76b943
1 changed files with 31 additions and 21 deletions
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52
src/http/modules/ngx_http_upstream_hash_module.c
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@ -49,8 +49,8 @@ static ngx_int_t ngx_http_upstream_get_hash_peer(ngx_peer_connection_t *pc,
static ngx_int_t ngx_http_upstream_init_chash(ngx_conf_t *cf,
ngx_http_upstream_srv_conf_t *us);
static void ngx_http_upstream_add_chash_point(
ngx_http_upstream_chash_points_t *points, uint32_t hash, ngx_str_t *server);
static int ngx_libc_cdecl
ngx_http_upstream_chash_cmp_points(const void *one, const void *two);
static ngx_uint_t ngx_http_upstream_find_chash_point(
ngx_http_upstream_chash_points_t *points, uint32_t hash);
static ngx_int_t ngx_http_upstream_init_chash_peer(ngx_http_request_t *r,
@ -360,12 +360,27 @@ ngx_http_upstream_init_chash(ngx_conf_t *cf, ngx_http_upstream_srv_conf_t *us)
ngx_crc32_update(&hash, (u_char *) &prev_hash, sizeof(uint32_t));
ngx_crc32_final(hash);
ngx_http_upstream_add_chash_point(points, hash, &peer->server);
points->point[points->number].hash = hash;
points->point[points->number].server = server;
points->number++;
prev_hash = hash;
}
}
ngx_qsort(points->point,
points->number,
sizeof(ngx_http_upstream_chash_point_t),
ngx_http_upstream_chash_cmp_points);
for (i = 0, j = 1; j < points->number; j++) {
if (points->point[i].hash != points->point[j].hash) {
points->point[++i] = points->point[j];
}
}
points->number = i + 1;
hcf = ngx_http_conf_upstream_srv_conf(us, ngx_http_upstream_hash_module);
hcf->points = points;
@ -373,28 +388,23 @@ ngx_http_upstream_init_chash(ngx_conf_t *cf, ngx_http_upstream_srv_conf_t *us)
}
static void
ngx_http_upstream_add_chash_point(ngx_http_upstream_chash_points_t *points,
uint32_t hash, ngx_str_t *server)
static int ngx_libc_cdecl
ngx_http_upstream_chash_cmp_points(const void *one, const void *two)
{
size_t size;
ngx_uint_t i;
ngx_http_upstream_chash_point_t *point;
ngx_http_upstream_chash_point_t *first =
(ngx_http_upstream_chash_point_t *) one;
ngx_http_upstream_chash_point_t *second =
(ngx_http_upstream_chash_point_t *) two;
i = ngx_http_upstream_find_chash_point(points, hash);
point = &points->point[i];
if (first->hash < second->hash) {
return -1;
if (point->hash == hash) {
return;
} else if (first->hash > second->hash) {
return 1;
} else {
return 0;
}
size = (points->number - i) * sizeof(ngx_http_upstream_chash_point_t);
ngx_memmove(point + 1, point, size);
points->number++;
point->hash = hash;
point->server = server;
}